Generally, image forming apparatuses are devised to form an image on a printing medium according to received image signals. Examples of image forming apparatuses include printers, copiers, facsimiles, and so-called multi-functional devices that combine some of the functionalities of the aforementioned devices.
In operation of an image forming apparatus, light is irradiated to a photosensitive body of a developing device that has been charged to a predetermined electrical potential, so as to form an electrostatic latent image on the surface of the photosensitive body. As toner, which is an example of developer, is supplied to the electrostatic latent image, a visible toner image is formed. The toner image formed on the photosensitive body is directly transferred to a printing medium or is indirectly transferred to the printing medium by way of an intermediate transfer body. The transferred image is fused to the printing medium via a fusing process.
The image forming apparatus further includes an electrical potential sensor to measure an electrical potential of the surface of the photosensitive body.
The developing device is separably mounted in the body of the image forming apparatus. When the electrical potential sensor is arranged close to the photosensitive body of the developing device, there may occur positional interference between the developing device and the electrical potential sensor during the installation or the separation of the developing device.